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This thesis reports the application of static and ramped electric fields to the Rydberg states of NO. Chapter 1 introduces the history of Rydberg states, their exotic properties, decay mechanisms, and the effect of an applied electric field. Chapter 2 details the experimental set-up used for the experiments presented in this thesis. Chapter 3 describes the structure of NO and multiphoton excitation scheme utilised for the work presented in this thesis. Chapter 4 investigates the effect of applied DC electric fields in the range 0 – 150 V cm-1 on the predissociating Rydberg states of NO below the υ+ = 0 ionisation limit, with principal quantum numbers n = 25 – 30. The Stark states are accessed by two-colour, double-resonance excitation via the υ′ = 0,N′ = 0, 1, 2, and 4 rovibrational states of the A2Σ+ state. The N (2D) atoms produced by predissociation are measured by (2 + 1) resonance-enhanced multiphoton ionization. The zero field and predissociation spectra are analysed using a matrix diagonalisation method. In Chapter 5, initial progress on simulating the spectra is presented. The predissociation spectra are compared with pulsed-field ionization spectra of the bound Rydberg state population providing an almost complete picture of the Rydberg state dynamics. In Chapter 6, ramped fields of varying slew rates are applied to the bound Rydberg states of NO, and the ionisation time profiles are obtained. The development of the experimental chamber and investigation into sources of electrical noise required to achieve this is discussed. It is shown that the rotational quantum state composition of field-ionised molecules can be controlled by varying the slew rate of the applied electric field.

In this PhD thesis the electronic structure of a range of actinide compounds has been investigated using density functional theory. The reason for using DFT instead of other methods is mainly due to the size of the compounds which makes multireference calculations prohibitively expensive, but also to make comparisons with previously calculated DFT results. The first chapter presents the basic concepts of electronic structure theory and the chemical properties of the actinides and lanthanides. The theoretical foundation of DFT and the consequences of relativity are also introduced. In the second chapter the bonding in mixed MUCl6, MUCl8 2-, NpReCl8 2- and PuOsC NpReCl8 2- (M = Mo, W) systems is investigated and compared with previous work on the M2Cl6, M2C NpReCl8 2- U2Cl6 and U2C NpReCl8 2- systems. The study shows that the total bonding energy in the mixed compounds is the average of the two “pure” compounds. The third chapter deals with systems of plenary or lacunary Keggin phosphomolybdate coordination to actinide (Th), lanthanide (Ce, La, Lu) and transition metal (Hf, Zr) cations: [PMo12O40]3-, [PMo11O39]2 14-, [PMo12O40]2 6- and [PMo11O39][PMo12O40]10-. These large, highly anionic systems proved to be very challenging computationally. The main result of the study confirms that the bonding is ionic and that there are few differences in the behaviour of the transition metals. In the fourth chapter the electronic spectrum of NpO2 2+, NpO2Cl4 2- and NpO2(OH)4 2- is calculated using time dependent DFT. TDDFT has proved adequate for the uranium analogues of these systems and this extends previous work on f0 systems to f1 systems. The results show that TDDFT is in poor agreement with both experimental results and multireference calculations for these compounds. In chapter five, group 15 and 16 uranyl analogues have been investigated. For the UE2 (E = O, S, Se, Te) analogues the geometry bends for all chalcogens heavier than O. The UE2 2+ analogues remain linear all the way down group 16. In U(NCH3)2 2+ the formation of a {pi} “back bone” along the axis of the molecule was noted. The {sigma}-bonding valence MOs stabilize while the {pi} MOs are destabilized down group 15 and 16. Chapter six is a summary of the results in this thesis and an outlook on potential future work.

The synthesis and characterisation of a range of oligo(aryleneethynylene)derivatives end-capped with cyanoethylthio and acetylthio groups are described. Sonogashira cross-coupling reactions have been key steps. These molecules are designed as molecular wires for conductance studies, including single-molecule conductance using Scanning Tunelling Microscopy (STM) and break junction techniques. Solution UV-V is absorption and fluorescence spectroscopy have been used to assess conjugation in the backbones, e.g. a sequential red shift is observed for molecules with 1, 2 and 3 fluorene units in the backbone (41 (RJ 11), 45 (RJ 13) and 47 (RJ 14); λ(_max) (abs.) 364, 371, 378nm, respectively) and a blue shift for molecules 35 (RJ 8) and 49 (RJ 17) is observed.The results of STM studies in Professor Ashwell's group (Bangor University) show symmetrical I-V characteristics for 35 (RJ 8), 41 (RJ 11), 43 (RJ 12) and 47 (RJ 14)assembled on gold. Preliminary STM results show length-independent current jumps for the molecules, which is inconsistent with theory: longer molecules should show lower conductance. The length independence suggests that the assembled molecules are being contacted by the STM tip along the backbone, not at the terminal sulfur. Most of the STM experiments show a single current jump, consistent with one molecule being contacted. However, some experiments with 43 (RJ 12) show double or even triple current jumps, suggesting simultaneous contact to two and three molecules. The conductance study of compound RJ 32 with I(t), I(s) and BJ techniques in Professor R. Nichols' group (Liverpool University) shows that the different techniques favour differing current peaks, with the BJ technique giving a higher propensity to higher current peaks, while the l(t)and I(s) method favour the lower current. A study using MCBJ experiments in Professor C. Schonenberger's group (University of Basel) show that oligo(phenyleneethynylene)(OPE) derivatives have lower conductance than oligo(phenylenevinylene) (OPV)analogues and alkoxy side chains on OPEs do not affect the single-molecule conductance.

The purpose of this project was to investigate cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analytical techniques for enantioselective sensing at both a macroelectrode and a microelectrode array. The scale of the electrochemical cell was reduced from macro to micro dimensions to improve both the electroanalytical detection and the efficient use of chemicals. A microdevice was fabricated using photolithography and plasma bonding and consisting of a microelectrode array (MEA) of 306 microelectrodes, each with a diameter of 45 µm supported by a polydimethylsiloxane (PDMS) slab engraved with microfluidic channels. The electroanalytical performances of the microdevice were characterised using cyclic voltammetry and it was established that the metallisation process influenced the surface roughness of the electrode, and also affected the final response of the array. The microdevice was used for flow injection analysis using chronoamperometry and provided the capability to detect small changes of analyte concentration. The selective electro-oxidation of phenylethanol catalysed by TEMPO and (-)-sparteine at a macroelectrode and MEA was investigated. The CV analysis showed a reproducible selective oxidation in favour of the (-)-phenylethanol enantiomer. The performances of the electrodes were enhanced to improve their enantioselective capability, and to extend their application to biosensors by functionalising their surface with Self-Assembled Monolayers (SAM). The electrodes were modified with glutathione and cysteine chiral molecules to investigate their ability to recognise the proline enantiomers using EIS analysis. The electron transfer rate of the ferricyanide analyte at the cysteine monolayer was less in the presence of D proline than it was in the presence of L-proline, indicating the selective penetration of the enantiomer through the monolayer. The properties of the macroelectrode and MEA were extended to biological applications by modifying their surfaces with thiolated single stranded DNA.

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